A DDOS, or a Dedicated Denial of Service attack, is when one person or multiple people launch millions of login or search requests on a dedicated server. When these happen, they can slow or even disable a network as they overload it with login requests and other demands. This particular attack targeted the various social media platforms, such as Facebook, Twitter and Instagram. It also appears that T-Mobile was the most hit of the telecoms as user reported issues connecting with that service provider especially in high population areas such as Texas and California.[1]
Such a dedicated attack on many tech giants is a reminder that no one is safe from cyber attacks. Vigilance and training are the best ways to detect and prevent such attacks. If you are the subject of an attack of this caliber, consult your cyber team about steps to contain it.
[1] https://www-the--sun-com.cdn.ampproject.org/c/s/www.the-sun.com/news/987168/ddos-attack-t-mobile-outage-facebook-instagram-us/amp/